1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. Furthermore, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, the present invention relates to, for example, a semiconductor, a semiconductor device, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, or a processor. Moreover, the present invention relates to a manufacturing method of a semiconductor, a semiconductor device, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, or a processor. The present invention relates to a driving method of a semiconductor device, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, or a processor.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A memory device, a display device, a light-emitting device, a lighting device, an electro-optical device, a semiconductor circuit, an electronic device, and the like include a semiconductor device in some cases.
2. Description of the Related Art
Much attention is focused on a semiconductor device that retains data even after interruption of power supply by using a combination of a transistor including semiconductor silicon (Si) in its channel formation region (this transistor is referred to as a Si transistor in the following description) and a transistor including an oxide semiconductor (preferably an oxide including In, Ga, and Zn) in its channel formation region (see Patent Document 1).
In recent years, with the increase in the amount of data manipulated, a semiconductor device having a large storage capacity has been required. In such situations, the semiconductor device disclosed in Patent Document 1 has a structure in which multilevel data is stored and read.